const btns = document.querySelectorAll('nav ul li')
const imgs = document.querySelectorAll('.content')

btns.forEach((btn, idx) => {
    btn.addEventListener('click', () => {
        btns.forEach( b => {
            b.classList.remove('active')
        })
        imgs.forEach( img => {
            img.classList.remove('show')
        })
        btn.classList.add('active')
        imgs[idx].classList.add('show')
    })
})